Among allergic diseases of the Korean pediatric population, allergic rhinitis shows the most rapidly increasing prevalence. Its economic burden is substantial in many Asian countries including South Korea. This investigation of its risk factors aims to reduce the socioeconomic burden by blocking exposure of susceptible individuals to identified causes. However, the risk factors of allergic rhinitis varied considerably depending on the seasons, geographical locations, and populations involved. This review article primarily deals with studies on the risk factors for allergic rhinitis in Korean children that were published during the last 10 years and additionally investigates associated large scale international studies. Our investigation identified several single-nucleotide polymorphisms, inhalant allergens, pollution, tobacco smoke, chemicals, and family affluence as risk factors for allergic rhinitis. In contrast, breastfeeding, older sibling, and microbial diversity were protective factors against allergic rhinitis. This suggests that various genetic and environmental factors might affect the manifestation and presentation of allergic rhinitis complexly. These findings are beneficial as they can provide insights into modifiable risk factors that may hinder the development of allergic rhinitis. (Allergy Asthma Respir Dis 2022;10:73-79)

HAE는 증상이 지속적이지 않고, 일반적인 검사에서는 이상 소견을 나타내지 않아 진단이 쉽지 않기 때문에 종종 진단이 지연된다. 하지만, HAE 환자는 정확한 진단과 적절한 대책이 없으면 위중한 결과에 이를 수 있으므로 신속, 정확한 진단과 대책이 중요하다. 한국에서의 HAE 유병률은 서양보다 상당히 낮으나, 최근 진단율이 증가하고 있다. 하지만, 국내에서 사용할 수 있는 약제에 제한이 있어, HAE 환자들의 정상적인 삶으로의 복귀를 위해 최신 치료 약제들의 국내 도입이 필요하다. 본 의견서를 통하여 진료일선에서 의심 환자를 선별하고, 이들에 대하여 적절하게 HAE를 진단하고 최적의 치료가 이루어지기를 기대한다.

Hereditary angioedema (HAE) is a rare disease, but it severely interrupts daily life activities and can sometimes be life-threatening. Therefore, early diagnosis and prompt treatment of HAE attacks are critical. Physicians should be aware of how to diagnose and manage HAE to prepare not to miss a diagnosis when treating HAE patients. Physicians must also carry out tests to confirm the diagnosis of HAEs caused by C1 inhibitor deficiency (type 1) or C1 inhibitor dysfunction (type 2) in patients with recurrent angioedema. In addition, recent studies revealed another type of HAE which is not related to C1 inhibitor (normal C1 inhibitor HAE). Once HAE is confirmed, patients and their caregivers should be given with short-term and long-term treatment plans to relieve or prevent HAE attacks. HAE requires life-long measures, including psychological support for patients and self-management education. (Allergy Asthma Respir Dis 2022;10:80-88)

Purpose: We investigated young children who developed bronchiolitis obliterans (BO) without preceding severe lower respiratory tract infection (LRTI).
Methods: Twenty patients referred for chronic respiratory symptoms and diagnosed with BO were enrolled and divided into 2 age groups: group 1 (<2 years, n=12) and group 2 (≥2, <6 years, n=8). A diagnosis of BO was made based on clinical and radiologic findings: (1) persistent cough or abnormal breath sounds which were not responsive to any treatment for more than 6 weeks; and (2) mosaic perfusion on high-resolution computed tomography. None of the subjects had experienced LRTI since birth, and those who had any underlying problems were excluded. The clinical characteristics and disease course were examined retrospectively.
Results: Mean age of the patients was 6.8 months and 3.4 years in group 1 and 2, respectively. All patients presented with chronic cough and the most common type of cough was mixed (wet and dry), 67% in group 1 and 50% in group 2. Persistent stridor was the major respiratory sign in group 1 (67%), but 63% of group 2 patients showed no abnormal breath sounds. Chest x-ray finding was nonspecific in 75% each of both groups. The respiratory symptoms and signs resolved rapidly in most patients treated with pulse corticosteroid therapy. Bronchial hyperresponsiveness and decreased forced expiratory volume in 1 second were observed in 3 of group 2 children at age 6, during the follow-up.
Conclusion: Our study shows that BO could develop without preceding severe LRTI. It also suggests that BO should be considered in the infants with persistent stridor accompanied by chronic cough. (Allergy Asthma Respir Dis 2022;10:89-96)

Purpose: This study aimed to analyze the immunologic profile of children with postinfectious bronchiolitis obliterans (PIBO) in order to approach pathophysiology affected by host factors.
Methods: A total of 10 children with PIBO were prospectively enrolled. We obtained information on demographics from their caregiver and electric medical records. Peripheral blood samples were collected before cyclic systemic methylprednisolone therapy and complete blood count, immunoglobulin level and lymphocyte subset were analyzed.
Results: The white blood cell count and immunoglobulin level were within the normal range in children with PIBO. The CD4+/CD8+ ratio was not significantly different from those of the healthy control group. A decreased proportion of both central memory T cells (median [interquartile range]; 13.5% [8.3%-16.3%] vs. 18.5% [15.9%-24.1%], P=0.01) and effector memory T cells (10.3% [5.0%-18.4%] vs. 20.9% [16.6%-26.3%], P=0.03) in CD4+T cells was observed in the PIBO group compared with those in the control group. In CD8+T cells, the proportion of effector memory T cells (7.8% [4.2%-13.8%] vs. 24.3% [15.3%-27.9%], P=0.02) and CD45RA+effector memory T cells (16.2% [11.0%-36.6%] vs. 24.2% [17.1%-39.7%], P=0.04) was decreased in the patient group compared with the control group.
Conclusion: It is suggested that T lymphocyte subset abnormalities may be associated with a decrease in the ability to differentiate the T cells immediately upon reinfection and induce an effective response to infection. These results may partially explain the pathophysiological individual vulnerabilities to PIBO after lower respiratory tract infections in children. (Allergy Asthma Respir Dis 2022;10:97-104)

Purpose: In food allergy, significant component antigens can be assessed by using the microarray. The purpose of this study was to evaluate the diagnostic value of component resolved diagnosis (CRD) in young children with kiwifruit allergy.
Methods: Through a retrospective review of medical records, we evaluated the clinical characteristics of 12 children who underwent measurement of serum immunoglobulin E concentrations to kiwifruit (kiwi-sigE) and were diagnosed as kiwifruit allergy. We applied ImmunoCAP ISAC-CRD 112 using the residual sera of patients at the initial visit.
Results: The median age of kiwifruit allergic children was 33.5 months (range, 13 to 84 months), and the proportion of systemic reactions, including 2 anaphylaxis cases, was 66.7%. Four had localized reactions on the lips. A total of 11 (91.7%) were sensitized to Act d 1; among them, 8 were mono-sensitized to Act d 1 and 3 were sensitized to ≥2 kiwifruit components. There was no significant difference in CRD results between those with systemic reactions and those with local reactions.
Conclusion: Act d 1 is the major allergenic component in Korean young children with clinical kiwifruit allergy. The additional diagnostic value of the CRD in diagnosing and predicting the severity of kiwifruit allergy is expected to be low in young children. (Allergy Asthma Respir Dis 2022;10:105-109)

Purpose: Perilla seed (PS) is the most common cause of seed-induced anaphylaxis in Korean children, but the reports on PS allergy, including phenotype and cross-reactivity, are rare. The aim of this study is to assess the clinical characteristics of PS allergy and investigate cross-reactivity with sesame seed (SS).
Methods: Through a retrospective medical record review, patients with clinical PS allergy were identified in a single tertiary hospital. Clinical characteristics of allergic reaction upon exposure to PS and SS, results of skin prick test (SPT) to PS and SS, and the levels of serum SS-specific immunoglobulin E (SS-sIgE) were investigated. Cross-reactivity between PS and SS was studied using IgE enzyme-linked immunosorbent assay (ELISA) inhibition.
Results: The median age of 34 PS-allergic children was 41.5 months (range, 10 months to 12 years), and the proportion of anaphylaxis upon exposure to PS was 29.4% (n=10). The PS SPT was positive in 94.1% (n=32) with the median wheal size of 6.25 mm. Among PS-allergic children, the percentages of patients with positive symptoms, negative symptoms, and indeterminate symptoms upon exposure to SS were 8.8%, 41.2%, and 50%, respectively. Out of 14 PS-allergic children who were tolerant to SS, positive sensitization to SS was noticed in 78.6% by serum SS-sIgE, and 57.1% by SS SPT. Partial cross-reactivity between PS and SS was identified in IgE ELISA inhibition.
Conclusion: This study reported the clinical profiles and SPT results in a relatively large number of PS-allergic children and identified the partial cross-reactivity between PS and SS for the first time. (Allergy Asthma Respir Dis 2022;10:110-117)

Subglottic cysts are rare but can cause significant airway obstruction that potentially threatens infants' lives. It is critically important to suspect subglottic cysts in infants with upper-airway obstructive symptoms because it can be treated effectively with only marsupialization without tracheostomy or complicated surgery. Here, we report an infant case of subglottic cyst, who showed prominent stridor and respiratory distress that abruptly progressed 2 months after extubation. The patient was born prematurely and had a history of endotracheal intubation in for a total of 16 days. He was stable with minimal stridor without respiratory distress until he was successfully discharged from the neonatal intensive care unit. However, he showed abrupt progress in stridor and respiratory difficulty about 2 weeks after discharge. Laryngoscopic exam revealed multiple subglottic cysts obstructing the trachea, and all of them were successfully removed by marsupialization. No recurrence of subglottic cysts was observed for 12 months thereafter. Subglottic cysts should be primarily suspected in infants with stridor, especially with a history of prematurity and intubation. Increased awareness of this fatal but curable condition is needed for timely and proper management. (Allergy Asthma Respir Dis 2022;10:118-122)

Acute pancreatitis (AP) rarely occurs in association with food allergy (FA), and the mechanism is not clearly explored. We herein report a rare case of egg protein-induced AP. A 5-year-old girl was brought to the hospital because of tongue pruritus and an increased level of egg white-specific immunoglobulin E. During an oral food challenge, she developed hives, abdominal pain and vomiting after ingestion of a cumulative of 610 mg of boiled egg white (70 mg of protein). After management with intramuscular injection of epinephrine and orally administered prednisolone and levocetirizine, her skin symptoms improved. The next day, blood tests showed elevated levels of amylase and lipase, and computed tomography revealed a swollen pancreas with a low-attenuated necrotic portion. She was diagnosed with AP and treated with food restriction, intravenous methylprednisolone and gabexate mesilate. The serum levels of amylase and lipase were reduced to normal levels on day 5 and her symptoms completely resolved on day 10. A suspicion of food-induced AP is required for correct diagnosis and proper management in children with FA when they manifest severe abdominal pain. (Allergy Asthma Respir Dis 2022;10:123-126)